The ABC head office is in security lockdown after receiving threats over Zaky Mallah's appearance on Q&A

The ABC offices in Sydney are operating on security lockdown protocols after threatening phone calls in relation to acquitted terror suspect Zaky Mallah’s appearance on its Q&A program.

An ABC spokesperson told Business Insider that it had received more than 1000 phone calls about the Q&A issue this week.

“Security has been stepped up at major ABC offices across Australia as a precautionary measure to protect the welfare of staff. There have been a number of threatening phone calls,” the spokesperson said.

The lockdown means the public, who often used the two entrances into the Ultimo building as a shortcut between Harris Street and Central train station, are unable to enter the building without permission.